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• Merge\Combine two datatables

  - by madlan

  I'm trying to merge\combine two datatables. I've looked at various examples and answers but they seem to create duplicate rows or require indexes (merge on datatable etc) I can't do this via SQL as one source is from a linked Oracle server accessed via MSSQL and the other from a different MSSQL Server that does not have linked access. The data is currently very simple: Name, Email, Phone DataTable1: "John Clark", "", "01522 55231" "Alex King", "[email protected]", "01522 55266" "Marcus Jones", "[email protected]", "01522 55461" DataTable2: "John Clark", "[email protected]", "01522 55231" "Alex King", "[email protected]", "" "Marcus Jones", "[email protected]", "01522 55461" "Warren bean", "[email protected]", "01522 522311" Giving a datatable with the following: "John Clark", "[email protected]", "01522 55231" "Alex King", "[email protected]", "01522 55266" "Marcus Jones", "[email protected]", "01522 55461" "Warren bean", "[email protected]", "01522 522311" Name is the field to match records on, with the first datatable taking priority.

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• OpenGL Wrapper in .Net

  - by Ngu Soon Hui

  This question is similar to the one here. But I feel that the answers recommended ( such as Tao and OpenTK) are not good enough because they are just a direct port from OpenGL, with no OOP design, and hard to use. What I'm looking for is a .Net OpenGL wrapper that is written in clear OOP principles, easy to use ( easy to apply textual and lighting, easy to debug etc), able to rotate the 3D diagram with mouse ( a feature that is critically missing from OpenGL and TAO), and the ability to export to other file formats ( such as dwg or dxf or Google Map file format). Any suggestion? Both Open source or commercial components would do.

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• How to configure a session timeout for Grails application?

  - by curd0

  In one of controllers in my Grails application I'm preserving a parameter value in a session variable like this: session.myVariable = params.myValue After that, I can access the saved value from different controllers/GSP-pages as long as I actively use the app. However, if I don't use my app for a while, even though my browser window is still open, the session variable looses it's value. Does this happens because the session expires? I was under impression that a session lives until the browser window is still open, but apparently I was wrong. What should I do to ensure all session variables I define in my Grails app don't expire until the browser is closed? Is there any way to set session timeout manually? Thank you in advance for your answers!

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• (R) How can I get the complement of vector y in vector x

  - by gd047

  That's x \ y using mathematical notation. Suppose x <- c(0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,1,2,1,1,1,3) y <- c(0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,1,1) How can I get a vector with ALL the values in x that are not in y. i.e the result should be: 2,1,1,3 There is a similar question here. However, none of the answers returns the result that I want.

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• MVVM framework AND Prism 4?

  - by Karsten

  I just read this question. It has some nice answers, but they are over 1 year old, and a lot have changed in this space over the last year. Some of the most popular frameworks have come out in a new mayor release such as Prism and MVVM Light Toolkit. My question is somehow the same, but with one twist, I'm already using Prism 4.0 because of the region and module features. Prism 4.0 embraces MVVM, but I feel there are something which are "not lightweight", for instance interaction requests. So I'm thinking would it better to use another MVVM framework either as a substitute or a supplement for Prism 4.0?

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• Customizing Rails XML rendering to include extra properties

  - by Isaac Cambron

  Let's say I have a model like this: create_table :ninjas do |t| t.string name end And the Ninja class with an extra property: class Ninja < ActiveRecord::Base def honorific "#{name}san" end end And in my controller I just want to render it to XML: def show render :xml => Ninja.find(params[:id]) end The honorific part isn't rendered. That makes sense, since it's just a method, but is there a way of tricking it? I'm totally up for answers to the effect of, "You're doing this totally wrong." I'll just add that I really do want to calculate the honorific on the fly, and not, like, store it in the database or something.

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• What are best practices for collecting, maintaining and ensuring accuracy of a huge data set?

  - by Kyle West

  I am posing this question looking for practical advice on how to design a system. Sites like amazon.com and pandora have and maintain huge data sets to run their core business. For example, amazon (and every other major e-commerce site) has millions of products for sale, images of those products, pricing, specifications, etc. etc. etc. Ignoring the data coming in from 3rd party sellers and the user generated content all that "stuff" had to come from somewhere and is maintained by someone. It's also incredibly detailed and accurate. How? How do they do it? Is there just an army of data-entry clerks or have they devised systems to handle the grunt work? My company is in a similar situation. We maintain a huge (10-of-millions of records) catalog of automotive parts and the cars they fit. We've been at it for a while now and have come up with a number of programs and processes to keep our catalog growing and accurate; however, it seems like to grow the catalog to x items we need to grow the team to y. I need to figure some ways to increase the efficiency of the data team and hopefully I can learn from the work of others. Any suggestions are appreciated, more though would be links to content I could spend some serious time reading. THANKS! Kyle

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• How can I write a clean Repository without exposing IQueryable to the rest of my application?

  - by Simucal

  So, I've read all the Q&A's here on SO regarding the subject of whether or not to expose IQueryable to the rest of your project or not (see here, and here), and I've ultimately decided that I don't want to expose IQueryable to anything but my Model. Because IQueryable is tied to certain persistence implementations I don't like the idea of locking myself into this. Similarly, I'm not sure how good I feel about classes further down the call chain modifying the actual query that aren't in the repository. So, does anyone have any suggestions for how to write a clean and concise Repository without doing this? One problem I see, is my Repository will blow up from a ton of methods for various things I need to filter my query off of. Having a bunch of: IEnumerable GetProductsSinceDate(DateTime date); IEnumberable GetProductsByName(string name); IEnumberable GetProductsByID(int ID); If I was allowing IQueryable to be passed around I could easily have a generic repository that looked like: public interface IRepository<T> where T : class { T GetById(int id); IQueryable<T> GetAll(); void InsertOnSubmit(T entity); void DeleteOnSubmit(T entity); void SubmitChanges(); } However, if you aren't using IQueryable then methods like GetAll() aren't really practical since lazy evaluation won't be taking place down the line. I don't want to return 10,000 records only to use 10 of them later. What is the answer here? In Conery's MVC Storefront he created another layer called the "Service" layer which received IQueryable results from the respository and was responsible for applying various filters. Is this what I should do, or something similar? Have my repository return IQueryable but restrict access to it by hiding it behind a bunch of filter classes like GetProductByName, which will return a concrete type like IList or IEnumerable?

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• Getting DataBinder Item's max value

  - by iTayb

  I'm working at the aspx page, and the following code is inserted in a Repeater control: <%# ((System.Collections.Generic.List<double>)DataBinder.Eval(Container.DataItem, "BookPrices")).Max() %> Brings up the following error: 'System.Collections.Generic.List<double>' does not contain a definition for 'Max' List does have an method of Max(), so I'm possibly messing up my code somehow. What is my problem? BookPrices is a list<double> object, which I'd like to print it's maximum value. P.S. You guys are great! I didn't find answers for many of my questions on the web. You really are life savers. Thank you very much! :)

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• Axis2 webservice (aar archive) properties file

  - by XpiritO

  Hi there, guys. I'm currently developing a set of SOAP webservices over Axis2, deployed over a clustered WebLogic 10.3.2 environment. My webservices use some user settings that I want to be editable without the need for recompiling and regenerating the AAR archive. With this in mind, I chose to put them into a properties file that is loaded and consumed in runtime. Unfortunately, I'm having some questions about this: As far as I know, to achieve what I want, the only option is to put the properties file into the ../axis2/WEB-INF/classes directory of each one of the deployments (on each WebLogic instance) I currently have on my clustered configuration, and then load the file, as follows (or equivalent, this has not been verified for optimization): InputStreamReader fMainProp = new InputStreamReader(this.getClass().getResourceAsStream("myfile.properties")); Properties mainProp = new Properties(); mainProp.load(fMainProp); This is not as practical as I wanted it to be, because each time I want to alter some setting on the properties file, I have to edit each one of the files (deployed over different WebLogic instances) and there is a high probability of modifying one of these files without modifying the others. What I would like to know is if there is any (better) alternative to accomplish what I want, minimizing the potential conflict of configuration that is created by distributing and replicating the properties file through multiple WebLogic instances.

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• Implementing Naïve Bayes algorithm in Java - Need some guidance

  - by techventure

  hello stackflow people As a School assignment i'm required to implement Naïve Bayes algorithm which i am intending to do in Java. In trying to understand how its done, i've read the book "Data Mining - Practical Machine Learning Tools and Techniques" which has a section on this topic but am still unsure on some primary points that are blocking my progress. Since i'm seeking guidance not solution in here, i'll tell you guys what i thinking in my head, what i think is the correct approach and in return ask for correction/guidance which will very much be appreciated. please note that i am an absolute beginner on Naïve Bayes algorithm, Data mining and in general programming so you might see stupid comments/calculations below: The training data set i'm given has 4 attributes/features that are numeric and normalized(in range[0 1]) using Weka (no missing values)and one nominal class(yes/no) 1) The data coming from a csv file is numeric HENCE * Given the attributes are numeric i use PDF (probability density function) formula. + To calculate the PDF in java i first separate the attributes based on whether they're in class yes or class no and hold them into different array (array class yes and array class no) + Then calculate the mean(sum of the values in row / number of values in that row) and standard divination for each of the 4 attributes (columns) of each class + Now to find PDF of a given value(n) i do (n-mean)^2/(2*SD^2), + Then to find P( yes | E) and P( no | E) i multiply the PDF value of all 4 given attributes and compare which is larger, which indicates the class it belongs to In temrs of Java, i'm using ArrayList of ArrayList and Double to store the attribute values. lastly i'm unsure how to to get new data? Should i ask for input file (like csv) or command prompt and ask for 4 values? I'll stop here for now (do have more questions) but I'm worried this won't get any responses given how long its got. I will really appreciate for those that give their time reading my problems and comment.

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• Objective-C : BOOL vs bool

  - by santoni

  Hi, I'm new to objective-c and I saw the "new type" BOOL (YES, NO). I read that this type is almost like a char. For testing I did : NSLog(@"Size of BOOL %d", sizeof(BOOL)); NSLog(@"Size of bool %d", sizeof(bool)); Good to see both display 1 (sometimes in C++ bool just an int and sizeof is 4) So I was just wondering I there were some issues with the bool type or something ? Can I just use bool (that seems to work) without loosing speed? Thanks for answers

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• DataMining / Analyzing responses to Multiple Choice Questions in a survey

  - by Shailesh Tainwala

  Hi, I have a set of training data consisting of 20 multiple choice questions (A/B/C/D) answered by a hundred respondents. The answers are purely categorical and cannot be scaled to numerical values. 50 of these respondents were selected for free product trial. The selection process is not known. What interesting knowledge can be mined from this information? The following is a list of what I have come up with so far- A study of percentages (Example - Percentage of people who answered B on Qs.5 and got selected for free product trial) Conditional probabilities (Example - What is the probability that a person will get selected for free product trial given that he answered B on Qs.5) Naive Bayesian classifier (This can be used to predict whether a person will be selected or not for a given set of values for any subset of questions). Can you think of any other interesting analysis or data-mining activities that can be performed? The usual suspects like correlation can be eliminated as the response is not quantifiable/scoreable. Is my approach correct?

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• Recursively CVS add files/directories and ignore existing CVS files.

  - by meder

  There's a similar post @ http://stackoverflow.com/questions/5071/how-to-add-cvs-directories-recursively However, trying out some of the answers such as: find . -type f -print0| xargs -0 cvs add Gave: cvs add: cannot open CVS/Entries for reading: No such file or directory cvs [add aborted]: no repository And find . \! -name 'CVS' -and \! -name 'Entries' -and \! -name 'Repository' -and \! -name 'Root' -print0| xargs -0 cvs add Gave: cvs add: cannot add special file `.'; skipping Does anyone have a more thorough solution to recursively adding new files to a CVS module? It would be great if I could alias it too in ~/.bashrc or something along those lines. And yes, I do know that it is a bit dated but I'm forced to work with it for a certain project otherwise I'd use git/hg.

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• JQuery UI sortable is slow in IE8, but works good in IE7 and IE8 compatible mode

  - by artvolk

  JQuery UI sortable (including demos) are slow in all IE8 I can test, but runs smoothly in IE7 and IE8 compatible mode. The more complex is a markup on the page, the more IE8 is slowing down (that's I can understand, the DOM tree became more complex). I'm using JQuery 1.3.2 and JQuery UI 1.7.2 (tested with 1.7.3 -- the same story). I've found a lot of similar reports (for the new JQuery UI 1.8.x with JQuery 1.4 too), but no answers. May be there is a some solution (EXCEPT turning IE8 into IE7 compatibility mode by metatag or header). Thanks in advance!

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• Mutating PDF editable fields programatically

  - by Chris

  Out of tons of questions and answers here about manipulating PDF's with PHP, but none of them seem to fit my requirement. Programmatically, I want to be able to update the content of editable fields. Preferably with PHP. If it matters, the PDF files will be initially hand crafted (as sort of 'template' files that will be copied and filled in over and over again). The list of PDF_* functions on php.net doesn't give me anything that looks (directly) promising. Is this possible with PHP? How?

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• Any way for a class to prevent outside code from declaring variables of its type?

  - by supercat

  Is it possible for a class of exposing a type for function returns, without allowing users of that class to create variables of that type? A couple usage scenarios: A Fluent interface on a large class; a statement like "foo=bar.WithX(5).WithY(9).WithZ(19);" would be inefficient if it had to create three new instances of the class, but could be much more efficient if the WithX could create one instance, and the other statements could simply use it. A class may wish to support a statement like "foo[19].x = 9;" even when foo itself isn't an array, and does not hold the data in class instances that can be exposed to the public; one way to do that is to have foo[19] return a struct which holds a reference to 'foo' and the value '19', and has a member property 'x' which could call "foo.SetXValue(19, 9);" Such a struct could have a conversion operator to convert itself to the "apparent" type of foo[19]. In both of these scenarios, storing the value returned by a method or property into a variable and then using it more than once would cause strange behavior. It would be desirable if the designer of the class exposing such methods or properties could ensure that callers wouldn't be able to use them more than once. Is there any practical way to accomplish that?

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• x86 opcode alignment references and guidelines

  - by mrjoltcola

  I'm generating some opcodes dynamically in a JIT compiler and I'm looking for guidelines for opcode alignment. 1) I've read comments that briefly "recommend" alignment by adding nops after calls 2) I've also read about using nop for optimizing sequences for parallelism. 3) I've read that alignment of ops is good for "cache" performance Usually these comments don't give any supporting references. Its one thing to read a blog or a comment that says, "its a good idea to do such and such", but its another to actually write a compiler that implements specific op sequences and realize most material online, especially blogs, are not useful for practical application. So I'm a believer in finding things out myself (disassembly, etc. to see what real world apps do). This is one case where I need some outside info. I notice compilers will usually start an odd byte instruction immediately after whatever previous instruction sequence there was. So the compiler is not taking any special care in most cases. I see "nop" here or there, but usually it seems nop is used sparingly, if at all. How critical is opcode alignment? Can you provide references for cases that I can actually use for implementation? Thanks.

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• Edit and Continue does not Work in VS 2010 / ASP.Net MVC 2

  - by Eric J.

  Although Enable Edit and Continue is checked on the Web tab of my ASP.Net MVC 2 project, I cannot in fact change the source code while running. For example, if I try to edit a controller while paused in the debugger, I cannot change the file (acts as if read only). I found a related post Edit and continue in ASP.NET web projects, however The answers seem to suggest I should be able to at least edit the code, then reload the page to see the result. I don't know what the distinction is between a Web Application and Web Site projects Any guidance is appreciated.

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• suggestions for Membership in ASP.NET MVC application

  - by mare

  With this question I am mostly looking for answers from people that have implemented the out-of-the-box ASP.NET membership in their own database - I've set up the tables inside my database and as far as I can see they contain mostly what I need but not everything. I will have the notion of a Firm (Company) to which Users will belong so I will have to associate the aspnet_Users with my Firms table (each user will be a member of exactly one firm). If possible, provide some guidelines how did you do it and what I might run into if I have to modify the table design at some point in the future. Preferably I will be using the default Membership provider. I am having trouble to decide whether to go from scratch or use what ASP.NET already offers.

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• Ajax Tab control in master page

  - by Senthilkumar

  Hi All I am using ajax tab container in master page with more than 4 tab panels, but when i include asp:contentplaceholder in content template of each tab panel i am not able to see the second or the third page (aspx) when i click on the tab.. i searched through net but didn get any answers. Pl help me. only the first page (aspx) included in content place holder is getting loaded the sencond asd so pages in tab panel are not// .. my example code here (.. only tis loaded) (.. not this one even when i clicked it)

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• Haskell Lazy Evaluation and Reuse

  - by Jonathan Sternberg

  I know that if I were to compute a list of squares in Haskell, I could do this: squares = [ x ** 2 | x <- [1 ..] ] Then when I call squares like this: print $ take 4 squares And it would print out [1.0, 4.0, 9.0, 16.0]. This gets evaluated as [ 1 ** 2, 2 ** 2, 3 ** 2, 4 ** 2 ]. Now since Haskell is functional and the result would be the same each time, if I were to call squares again somewhere else, would it re-evaluate the answers it's already computed? If I were to re-use squares after I had already called the previous line, would it re-calculate the first 4 values? print $ take 5 squares Would it evaluate [1.0, 4.0, 9.0, 16.0, 5 ** 2]?

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• Programmatically creating vector arrows in KML

  - by mettadore

  Does anyone have any practical examples of programmatically drawing icons as vectors in KML? Specifically, I have data with a magnitude and an azimuth at given coordinates, and I would like to have icons (or another graphical element) generated based on these values. Some thoughts on how I might approach it: Image directory (a brute force way): Make an image director of 360 different image files (probably batch rotate a single image) each pointing in a cooresponding azimuth. I've seen things like "Excel to KML," but am looking for code that I can use within a program, rather than a web utility. Issue: Arrow does not contain magnitude context, so that would have to be a label. I'd rather dynamically lengthen the arrow. Line creation in KML: Perhaps create a formula that creates a line with the origin at the coordinate points, with the length of the line proportional to the magnitute, and angled according to azimuth. There would then be two more lines, perhaps 30 degrees or so extending from the end of the previous line to make the arrow head. Issues: Not a separate image icon, so not sure how it would work in KML. Also not sure how easy it would be to generate this algorithm. Separate image generation: Perhaps create a PHP file that uses imagemagick or something similar to dynamically generate a .png file in a similar method to the above, and then link to the icon using the URI "domain.tld/imagegen.php?magnitude=magvalue&azimuth=azmvalue". Issue: Still have the problem of actually writing the algorithm for image generation. So, the question: has anyone else come up with solutions for programmatic vector (rather than merely arrow) generation?

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• Best reverse proxy for IIS 6?

  - by Chris

  I want to set up a reverse proxy from one of our intranet IIS sites to point to another tomcat server. Eg, i want the user to browse to 'http://our-iis-server/friendly-url' and for it to reverse proxy to 'http://our-tomcat-server/ugly-url'. What would be the best solution for this? I've narrowed it down to three options: http://www.managedfusion.com/products/url-rewriter/documentation.aspx http://www.isapirewrite.com/ http://www.codeplex.com/IIRF Also, can these tools rewrite the links in the html? Eg, if the tomcat server's html has something like 'a href = http://our-tomcat-server/ugly-url/product/widget' i would need it to change to 'a href = http://our-iis-server/friendly-url/product/widget' Thanks in advance. All good answers will be voted for!!!

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• Worse is better. Is there an example?

  - by J.F. Sebastian

  Is there a widely-used algorithm that has time complexity worse than that of another known algorithm but it is a better choice in all practical situations (worse complexity but better otherwise)? An acceptable answer might be in a form: There are algorithms A and B that have O(N**2) and O(N) time complexity correspondingly, but B has such a big constant that it has no advantages over A for inputs less then a number of atoms in the Universe. Examples highlights from the answers: Simplex algorithm -- worst-case is exponential time -- vs. known polynomial-time algorithms for convex optimization problems. A naive median of medians algorithm -- worst-case O(N**2) vs. known O(N) algorithm. Backtracking regex engines -- worst-case exponential vs. O(N) Thompson NFA -based engines. All these examples exploit worst-case vs. average scenarios. Are there examples that do not rely on the difference between the worst case vs. average case scenario? Related: The Rise of ``Worse is Better''. (For the purpose of this question the "Worse is Better" phrase is used in a narrower (namely -- algorithmic time-complexity) sense than in the article) Python's Design Philosophy: The ABC group strived for perfection. For example, they used tree-based data structure algorithms that were proven to be optimal for asymptotically large collections (but were not so great for small collections). This example would be the answer if there were no computers capable of storing these large collections (in other words large is not large enough in this case). Coppersmith–Winograd algorithm for square matrix multiplication is a good example (it is the fastest (2008) but it is inferior to worse algorithms). Any others? From the wikipedia article: "It is not used in practice because it only provides an advantage for matrices so large that they cannot be processed by modern hardware (Robinson 2005)."

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